Hexa-armed and thiophene (Thi) end-capped poly(epsilon-caprolactone) star polymer (N3P3-(PCL-Thi)(6)), containing cyclotriphosphazene core, was prepared in a four-step reaction sequence. Ring-opening polymerization (ROP) and "click chemistry" techniques were employed in the first and final steps, respectively. Hexa-armed PCL star polymer (N3P3-(PCL-OH)(6)) was successfully synthesized via ROP of epsilon-caprolactone (epsilon-CL) by using hekzakis(p-(hydroxymethyl)phenoxy) cyclotriphosphazene as the multisite initiator and tin(II) 2-ethylhexanoate (Sn(Oct(2))) as the catalyst in bulk at 115 degrees C. Further modifications of the N3P3-(PCL-OH)(6) were accomplished by derivatization of the hydroxyl-functional chain ends. The obtained N3P3-(PCL-OH)(6) was then reacted with 2-bromo-2-methylpropanoyl bromide, and this led to a star polymer with bromide end groups, N3P3-(PCL-Br)(6). In the third step, N3P3-(PCL-Br)(6) was azidified with sodium azide (NaN3) in DMF affording N3P3-(PCL-N-3)(6). Conversion of the azide chain end groups into Thi was quantitatively accomplished via the "click reaction" between N3P3-(PCL-N-3)(6) and prop-2-yn-1-yl 3-thienyl acetate in the final step. Subsequently, the star polymer with six Thi chain ends (N3P3-(PCL-Thi)(6)) was employed in electrochemical copolymerization with both pyrrole and Thi. Electrochromic properties and electrochromic device application of N3P3-(PCL-Thi)(6)/PThi were also investigated. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3668-3682, 2010